maybe some one with more knowledge will answer.i would use dirt and lily tabs lotus are heavy feeders.i would not use cow manure i think it would discolor the water

No experience either, but I suppose it depends on the source. I have used dump truck loads of well composted cow manure all over my yard. It really looks like soil and I doubt that it would cause problems as long as it was covered with something like cat litter etc.

You can over do it with manure. I lost some Lotus like that. Possibly the manure wasn't aged enough but it's made me more cautious with it.

I have several pots so I put some with dirt and some with half and half...will let you know how I go.